GREENFIELD — The Planning Board has approved several proposed zoning amendments to the city’s cluster development ordinance in an effort to balance open space with a push to grow its housing stock.

The city’s cluster development ordinance allows developers to build dense single, two-family and multi-family housing on a small portion of open space in the city’s Urban Residential, Suburban Residential and Rural Residential districts.

According to Planning Board Chair George Touloumtzis, the proposed changes were drafted alongside representatives from the Franklin Regional Council of Governments (FRCOG) to densify housing in the city’s more rural areas.

“This form of development would apply to certain areas that have enough room for it, so it’d be in the more rural parts of town,” Touloumtzis said. “The idea is to, rather than have individual homes and yards dominating the landscape, have more of a balance of the natural environment with the built environment.”

The ordinance’s proposed amendments allow the Planning Board, through the special permit process, to grant unit “density bonuses” to developers whose proposed projects contain design features that align with the city’s Master Plan.

Under the proposed changes, the city would be able to allow developers to build 10% more housing units than otherwise allowed if more than 20% of the units are designated as affordable under Chapter 40B.

Other design features that can earn a developer extra units include the creation of senior affordable housing; net-zero carbon sustainability; extra protection of land, trees or wildlife; and the orientation of rooftops to accommodate the installation of solar panels.

“Density bonuses are some of these certain categories of things that the board felt are in the interest of the community,” Touloumtzis said. “The idea is to provide a form of development that will both reward the preservation of open space, but also encourage density of housing so that housing needs are met as well — the housing needs of both the animals and the people.”

The proposed amendments also alter the formula with which the number of dwelling units allowed on a development is calculated to subtract only 10% — rather than the entirety — of the acreage subject to restrictions, such as Federal Emergency Management Agency floodplains, wetlands or local restrictions from the proposed project’s total acreage.

It also would subtract only 10% the total acreage of land with slopes of 25% or greater, rather than 50%.

Working with FRCOG’s Senior Land Use and Natural Resource Planner Allison Gage, the Planning Board met last week to finalize the proposed amendments.

In its discussions, the board debated the ratio of sloped or protected land that could be classified as open space in the calculation of the number of units allowed on a site.

Although Gage and Planning Director Eric Twarog both suggested that changing the percentage of open space subtracted from total calculations from 100% to 10% would make for too dramatic a shift, board members Sara Brown-Anson and Victor Moschella both supported the 10% option, with Moschella arguing that wetlands being discounted as open space was “entirely unfair.”

“We don’t believe that any land should be completely taken out of the calculation because you’re still protecting it,” Moschella said.

After Twarog noted that the calculations would not be applicable in the areas likely to be developed in Greenfield, the board unanimously voted to finalize the ordinance draft with the rate set at 10%.

Touloumtzis said the board will meet with the Economic Development Committee for a public hearing in the coming months, with the goal of bringing the amended ordinance before City Council in either September or October.

Anthony Cammalleri can be reached at acammalleri@recorder.com or 413-930-4429.